The present invention relates to a muscle stimulation method and apparatus and particularly to a method and apparatus for selectively initiating electrical stimulation in synchronism with certain body movements.
As the result of trauma or surgery, an individual can lose the strength of certain muscles and/or atrophy may occur because of nonuse or confinement in a cast. Physical therapy may be prescribed, including muscle exercise for regaining the lost muscle function. A particular exercise may be defined as isometric wherein the patient exerts force against a fixed object, or isokinetic wherein the patient pushes or pulls against a moving or movable object which has a maximum allowable speed.
In an isokinetic exercise machine known as a dynamometer, a rotatable arm is moved by the patient, wherein the arm is resistive to movement at greater than a preset speed. The patient may exert whatever force he desires at such speed. However, the patient can slow his movement or discontinue movement altogether, e.g. if pain develops, and the machine is constructed for thereupon discontinuing its resistive force. This cessation in resistive force would not occur, for example, if a weight were simply attached to the limb being exercised. Although isokinetic exercise of this type is quite valuable for therapy purposes, nevertheless many patients lack the ability to initiate muscle contraction over either all or part of a normal range of movement, or their ability is so marginal that therapy for muscle restoration is a slow process.
Electrical stimulation can be employed for initiating muscular contraction, especially in patients who have lost motor nerve control. However, electrical stimulation in the past has been employed substantially independently of, rather than in coordination with, mechanical exercise devices. Stimulation has also not been accurately and selectably synchronized with ranges of bodily movement.